<form action="/form/create" method="POST">
    <p>Check one or more colors</p>

    <label for="red">Red</label>
    <!-- name can be "colors" too -->
    <input type="checkbox" name="colors[]" value="red" id="red">
    <label for="green">Green</label>
    <input type="checkbox" name="colors[]" value="green" id="green">
    <label for="blue">Blue</label>
    <input type="checkbox" name="colors[]" value="blue" id="blue">
    <input type="submit">
</form>
